In general, in a valve configured to perform a disc opening/closing function through vertical movement of a stem, a lower portion of the stem is submerged in a fluid such as a high pressure vapor, water, oil, or the like, an upper portion of the stem is connected to a handle configured to move the stem, or the like, and a packing is provided to prevent leakage of the fluid from the lower portion of the stem through an outer circumferential surface of the stem. The packing, which is a consumable part configured to seal the valve, loses its sealing performance due to repeated vertical movement of the stem. A decrease in sealing performance means that, in particular, radioactive contamination may occur from a nuclear power plant, and accordingly, a device for effectively exchanging a packing having a decreased sealing performance in a state of preventing such contamination is needed.
Detailed description of individual members of the valve according to the related art, which is technology known to those skilled in the art, will be omitted in the specification.
Two methods of removing the packing 430 from the valve of the related art are proposed. A first method of exchanging the packing in a state in which all of a stud bolt, a stud nut, a guide bushing, a beveled washer, a guide ring, a packing flange and a gland bushing are removed, and a second method of exchanging the packing in a state in which the stud bolt and the stud nut are removed and a stem is moved upward to closely attach a disc to a bonnet are provided. Since a fluid in a pipe should not be leaked during exchange of the packing in a nuclear power plant, an oil refining plant, or a chemical plant, the second method is used. In this method, after removing the stud bolt and the stud nut, the stem, the packing flange and the gland bushing are moved upward, and a high pressure of water or air is injected using a special tool for packing removal (a hydro pic) to raise the packing, removing the packing. Selectively, in a valve including a lantern ring and a leakage collecting flow path to collect leakage, the lantern ring can also be removed in the same manner as the packing.
When the packing is removed by the second method, in order to prevent leakage through a special tool mounting flow path, a flow path inlet should be re-welded or a cover should be tightly fastened to prevent the leakage. Due to the leakage risk, in the case of some valves used in the nuclear power plant or the chemical plant, after a valve disc is moved upward to be closely attached to a valve body to prevent leakage without using the special tool for packing removal, the stud bolt and the stud nut are removed, the stem, the packing flange 460 and the gland bushing are moved upward to obtain a working space, and then the packing and the lantern ring are extracted using a packing removal tool (not shown). In this case, since the working space that can be obtained by moving the packing flange and the gland bushing upward is very narrow and limited, the work becomes difficult, and tangling is generated within the packing to cause limitation in removal of the packing such as damage to the packing. In addition, since the packing removal tool formed of a metal material scratches the stem during removal of the packing, slight leakage may be generated through the scratches even when a new packing is mounted.